Boarded Biblical boat inside plant (8)
I believe the answer is:
embarked
'boarded' is the definition.
(embarking is a kind of boarding)
'biblical boat inside plant' is the wordplay.
'biblical boat' becomes 'ark' (I've seen this before).
'inside' indicates putting letters inside.
'plant' becomes 'embed' (I've seen this before).
'ark' going within 'embed' is 'EMBARKED'.
(Other definitions for embarked that I've seen before include "Set out on a voyage" , "Began (on project)" , "Went on board ship or plane" , "Got on" , "Having set sail" .)